The present invention relates to a method and an arrangement for preventing overturning a dump vehicle.
In connection with transportation of heavy loads, e.g. in contracting work, dump vehicles of the type of articulated haulers (also called frame-steered vehicles or dumpers) are frequently used. Such vehicles may be operated with large and heavy loads in areas where there are no roads, for example for transports in connection with road or tunnel building, sand pits, mines and similar environments.
A dump vehicle comprises a forward vehicle section (a so-called engine unit) which in turn comprises a forward frame, an engine, a cab, and a forward wheel axle supported by the frame. The dump vehicle further comprises a rear vehicle section (a so-called load-carrying unit) which in turn comprises a rear frame, a tiltably arranged container for carrying loads, and one or two rear wheel axles supported by the frame.
The frame of the engine unit is connected to the frame of the load-carrying unit by means of a special articulation joint allowing the engine unit and the load-carrying unit to pivot in relation to each other about an imaginary axis extending in the longitudinal direction of the vehicle. Thanks to the articulation joint, the engine unit and the load-carrying unit are allowed to move substantially independently of each other, which reduces stress loads acting on the vehicle, especially when operating in difficult terrain.
When the dump vehicle is unloaded in certain situations, there is a risk for overturning the forward vehicle section. More specifically, when the container is tilted, the material in the container may stick to the container. The centre of gravity of the dump vehicle will then move backwards. If the pair of wheels of the rearmost axle of the load-carrying unit does not have proper contact with the ground, there is a risk that the dump vehicle will rise and tilt backwards. In other words, the dump vehicle would in such a case rotate around a ground contact point defined by the pair of wheels on the forward wheel axle of the rear vehicle section. The wheels of the forward vehicle section would then lose ground contact and there is a risk for the forward vehicle section, which comprises the cab for an operator, to rotate in an uncontrolled manner around the articulation joint between the forward vehicle section and the rear vehicle section, which of course could lead to material damages and/or injuries.
It is desirable to achieve a method and an arrangement for preventing a turn-over of a dump vehicle with an articulation joint, which connects a forward frame and a rear frame, allowing the forward frame and the rear frame to pivot in relation to each other about an axis extending in a longitudinal direction of the vehicle.
A method according to an aspect of the present invention involves steps including, during a tilting procedure for unloading material from a container of the dump vehicle, determining if there is a risk for a pair of wheels of the wheel axle of the forward vehicle section to lose ground contact or if said pair of wheels have already lost ground contact, and establishing a warning signal for preventing an uncontrolled rotation of the forward vehicle section relative to the rear vehicle section via the articulation joint when it is determined that the wheels of the forward wheel axle has lost or is about to lose ground contact.
The wording “tilting procedure for unloading material from the container” not only comprises the time onwards from the actual motion start but also the time in preparation for the actual tilting motion. Thus, the wording “preventing unloading of material” comprises both preventing start of a tilting motion of the container and preventing continuation of, i.e interrupting or stopping, an already started tilting motion.
According to an aspect of the invention, the method comprises the step of determining if at least one wheel in a pair of wheels on the wheel axle supported on the rear frame loses, or is about to lose, ground contact, and using this information for determining the risk for the wheels of the wheel axle of the forward vehicle section to lose ground contact. Thus, for the specific type of vehicle with two bogie axles on the rear vehicle section, the knowledge that there is a high risk for raising the vehicle when only the wheels of one of the bogie axles have ground contact, is used.
According to an aspect of the invention, the method comprises the step of sensing an inclination of a bogie element, which is pivotably suspended in a frame beam of the rear vehicle section, and using this information for determining the risk for the wheels of the wheel axle of the forward vehicle section to lose ground contact.
According to an aspect of the invention, the method comprises the step of receiving said warning signal and automatically preventing tilting of the container. This may be achieved by hindering a supply of hydraulic fluid to a hydraulic tilting means, which is arranged between the rear frame and the container for tilting the container relative to the rear frame.
Further features of the invention and advantageous effects thereof will be apparent from the further claims and the following description.